The present invention relates to a filtration and pressure stabilization device for a variable-flow ventilation system.
It is known that ventilation systems can be made to have a variable flow, either to provide heat loads with a variable value, or to modify the flow as a function of the needs of the premises to be ventilated. It is also known, particularly in office buildings or industrial buildings, that forced-air ventilation can be provided, allowing the flow to be controlled in each room. It is advantageous to have a filter ahead of the fan, which can purify the air blown into the various rooms.
It should be noted that the filter introduces variations in the value of the pressure available hence variations in the value of the flow, which affects the desired flow.
A first solution in maintaining the desired flow consists of regularly cleaning the filters. However, this cleaning is an expensive maintenance operation and does not fully stabilize the pressure, since even if the filter is replaced before it is completely clogged, the value of the pressure available will vary depending on how much dirt the filter has accumulated.
There are also roll-type filters, namely filters with a greater length than the length of the air inlet opening with which the filter is associated, this roll-type filter cooperating with a supply roller and a takeup roller which are driven synchronously at regular time intervals.
Other than the fact that the roll-type filter does not ensure full pressure stabilization, it requires frequent replacement to prevent clogging which results in a high operating cost.
German Patent DE-A-2,338,048 relates to a device having a roll-type filter with which a variable-position shutter is associated. The goal of this device is to neutralize a useful part of the filter when the ventilation flow decreases. Thus, the idea is automatically to adjust the filter surface area to variations in flow, without taking into account the dirtiness of this filter surface. Thus, when the flow is far from the maximum capacity of the filtration device, and the exposed filter surface offers too much air resistance because it is dirty, the filter is replaced instead of exposing a larger filter surface. Thus, this control method affords no filter economies whatever.